Thermotropic Polypeptides. 6. On Cholesteric Mesophase with Grandjean Texture and its Solidification

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Abstract
The domain texture was examined for thin cholesteric mesophases (∼20 pm) of the thermotropic polypeptides which were placed between glass plates by giving a shear flow under pressure. The optical microscopy shows the Grandjean monodomain texture for these thin mesophases and the electron microscopy (TEM method) clarifies its direct structure, having a regular stack of cholesteric layers lying parallel to the film plane. The easy preparation of the Grandjean texture is characteristic of polypeptide cholesterics and can be attributed to a preferential planar orientation of rigid-rod molecules with their long axes lying parallel to a glass surface. Solid Grandjean cholesteric films could be prepared by quenching the mesophases and retained beautiful cholesteric colors if cholesteric mesophases with small pitches were treated. The color of solid cholesteric which arises in a narrow band region less than 30 nm is insensitive to temperature variation and stable for a long time (beyond years). Some applications of the optical properties of solid Grandjean cholesteric films are suggested.